Originally Posted By: greenjp
Originally Posted By: Tegger
There are a couple of things you can do to prolong the life of your new cat. Ask here if you wish to know what they are.
I'd love to. I'm curious because my 2003 Saab 9-5 with 157k miles is still on the original cat. Actually the entire exhaust system on that car is original. Not doing anything differently with the Accord but am open to suggestions!
The key to maximum cat life is to have as complete combustion as possible at each combustion event. Poor combustion results in much larger amounts of raw gas entering the cat than the cat was intended to handle, and each poor-combustion event causes a tiny amount of damage. A poor-combustion event is known as a "misfire", whether you feel anything or not as it happens. Misfire damage accumulates over the years and appreciably shortens cat life. The OBD-II system is pretty good at detecting misfires, but misfire codes only set once misfire events reach a certain threshold.
The important thing to remember is that misfire damage is cumulative. Cumulative cat-damage will occur at misfire levels below that which would trigger misfire error-codes. A situation that results in one misfire is just about guaranteed to result in many over time, if not corrected.
Catalytic converter surfaces are extremely porous, sort of like a sponge, in order to produce maximum reactive surface-area within the volume of the element. Misfires damage the cat by causing that porous surface to melt and erode, which greatly reduces reactive surface-area.
Four things you can do to prevent those damaging misfires are to:
1) never allow the gas tank level to get too low, or to run dry;
2) pay very particular attention to ignition high-tension system maintenance, servicing it at least as often as the manual says, and more often if possible;
3) use only OE (genuine Honda) engine/ignition parts;
4) perform proactive inspection of your EGR system (if so equipped).
Your Honda's Owner Manual should warn you against the first. If the gas tank level gets too low--and this can occur well before the low-fuel light comes on--the possibility increases of the fuel pump briefly but repeatedly sucking air. Each time this happens, fuel-pressure drops enough to cause lean-misfires which dump raw gas into the cat. The MIL will not illuminate when this happens, and you may not feel anything wrong.
Running out of gas is the worst thing you can do to the cat, since that results in an extended series of misfires as the fuel pump fights to maintain pressure and the engine keeps stuttering and running.
Worn, aged, or poor-quality aftermarket ignition components can cause misfires, and can also throw extra load on the coils.
Clogged EGR passages (from the EGR valve to the cylinders) can also cause misfires, if the blockages result in only one or two cylinders being denied exhaust gases(which usually means the others are receiving an excess). This is not necessarily detected by the OBD-II system, but will show up as elevated NO and HC in an emissions test.
